High-density metal capacitor using dual-damascene copper interconnect

ABSTRACT

An electronic structure having a first conductive layer provided by a dual damascene fabrication process; an etch-stop layer provided by the fabrication process, and electrically coupled with the first conductive layer, the etch-stop layer having a preselected dielectric constant and a predetermined geometry; and a second conductive layer, electrically coupled with the etch-stop layer. The structure can be, for example, a metal-insulator-metal capacitor, an antifuse, and the like.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This patent application is a continuation of U.S. patentapplication Ser. No. 09/971,254 filed Oct. 3, 2001 which claims thebenefit of the filing date of U.S. Provisional Patent Application SerialNo. 60/237,916, filed Oct. 3, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention herein relates to the formation of an integratedcircuit including a capacitor. More specifically, this invention relatesto the formation of a metal-insulator-metal capacitor in an integratedcircuit.

[0004] 2. Description of the Related Art

[0005] As integrated circuit (IC) complexity increases, the number ofinterconnections used in an IC increases accordingly. IC fabricationmethods providing layouts multiple metal layer layouts have becomepopular techniques for accommodating increased number ofinterconnections in such ICs. Because highly-integrated ICs facedifficulties meet the requisite yield and interconnect reliabilityrequirements, newer methods and structures have been developed andapplied in the semiconductor fabrication process. Two recently-developedfabrication techniques include the single damascene process and the dualdamascene process. Single damascene is an interconnection fabricationprocess in which grooves are formed in an insulating layer and filledwith metal, for example, copper, to form the conductive lines. Dualdamascene is a multi-level interconnection process in which conductivevia openings are formed in addition to forming the grooves of singledamascene. Dual damascene is an improvement over single damascenebecause it permits the filling of both the conductive grooves and viaswith metal at the same time, thereby eliminating process steps. Becausea dual damascene structure satisfies the requirement of low resistanceand high electromigration, it has been widely used in deep sub-micronVLSI fabrication processes for obtaining an efficient and reliableinterconnections. In fabricating very and ultra large scale integration(VLSI and ULSI) circuits with the copper dual damascene process,insulating or dielectric materials are patterned with several thousandopenings for the conductive lines and vias, which are filled at the sametime with metal, and serve to interconnect the active and/or passiveelements of the integrated circuit. However, dual damascene processesusing copper metal fill can make device fabrication a daunting task.Copper is a known fast-diffuser and can act to “poison” a device,creating a failure, once it gets into the active area (i.e.,source/drain/gate region of the transistor). This has required thedevelopment of new and advanced diffusion barriers to eliminate thatthreat, as well as different fab layouts to isolate the copperproduction part of the line from the rest of manufacturing.Metal-insulator-metal (MiM) capacitors are generally used inhigh-density integrated circuits in a variety of applications. Forexample, metal-electrode capacitors are widely used in mixed-signal/RFintegrated circuits because of their better linearity and higher Q (dueto lower electrode resistance) relative to other IC capacitorconfigurations. Metal-insulator-metal (MiM) capacitors have beencommercially available in the standard CMOS mixed-signal process withaluminum interconnects, by adding a few additional steps to thetraditional process flow. Present MiM fabrication techniques in dualdamascene processes typically involve additional fabrication steps inwhich extra barrier and dielectric layers needed to form such devicestend to complicate an already difficult and expensive process. What isneeded, then, is a MiM capacitor which can be reliably fabricated withfewer process steps using standard materials, preferably eliminating theadditional fabrication steps typically associated with creating suchdevices.

SUMMARY OF THE INVENTION

[0006] The present invention solve the aforementioned limitations of theprior art by providing an electronic structure, having a firstconductive layer provided by a predetermined fabrication process; anetch-stop layer provided by the predetermined fabrication process, theetch-stop layer electrically coupled with the first conductive layer,the etch-stop layer having a preselected dielectric constant and apredetermined geometry; and a second conductive layer, electricallycoupled with the etch-stop layer. The preselected dielectric constant ispreferred to be above about 4.0, or a relatively “high-k” dielectricvalue. The etch-stop layer is employed as the capacitor dielectric. Theetch-stop layer can be a silicon nitride having a preselected dielectricconstant of between about 5.5 and about 9.0. Also, the predeterminedfabrication process is desired to be a dual damascene fabricationprocess, such as a via-first dual damascene process, where at least oneof the first and second conductive layers comprises a metal. Theelectronic structure of the present invention is described forconvenience in terms of a metal-insulator-metal capacitor, but theprinciples herein also can be employed to fabricate a multiplicity ofconductor/dielectric structures, including, for example, an antifuse.Furthermore, the structure can be formed from horizontally- andvertically-disposed regions to create the desired aggregate capacitanceor other desired electrical characteristics.

[0007] The semiconductor device of the present invention employsexisting fabrication processes, and in particular the existing etch stoplayers, to fabricate the desired devices and structures, therebyminimizing cost and increasing the relative density of desired physicaland electrical characteristics. Such a device can include a dielectricmatrix with a dielectric constant having a first dielectric value, forexample of a low-k (k<about 4.0) dielectric. Selectively disposed withinthe dielectric matrix are conductive regions, such as metals or organicconductors, each of the conductive regions having a predetermined shape,and being set apart in at least one of a horizontal direction and avertical direction, relative to others of the conductive regions.Selected ones of the conductive regions are conductively intercoupledusing interconnected metal/via layers. The device also includes etchstop regions selectively disposed within the dielectric matrix. Each ofthe conductive regions have a predetermined shape, and are set apart inat least one of a horizontal direction and a vertical direction relativeto others of the conductive and etch stop regions. Selected ones of theetch stop regions are interposed between respective conductive regions.The etch stop regions have dielectric constants having a seconddielectric value, which are effectively greater than the firstdielectric values, for example k>5.0. Selected others of the conductiveregions, separated by selected ones of the etch stop regions, arecapacitively intercoupled by the selected etch stop regions. A firstelectrode is electrically coupled with a predetermined one of theselected conductively intercoupled conductive regions; and a secondelectrode is electrically coupled with a predetermined one of theselected others of the conductive regions, separated by selected ones ofthe etch stop regions, and capacitively intercoupled by the selectedetch stop regions. Such a semiconductor device can be readily adapted toa metal-insulator-metal capacitor, and antifuse, or a multiplicity ofother conductor/dielectric components and devices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The patent or application file contains at least one drawingexecuted in color. Copies of this patent application publication withcolor drawing(s) will be provided by the Office upon request and paymentof the necessary fee.

[0009] These and other features, aspects and advantages of the presentinvention will be more fully understood when considered with respect tothe following detailed description, appended claims and accompanyingdrawings, wherein:

[0010]FIG. 1a is a partially-fabricated embodiment of a semiconductordevice according to the present invention after the formation of vias;

[0011]FIG. 1b is a partially-fabricated embodiment of the semiconductordevice in FIG. 1a, after the addition of a trench-patterned photoresistlayer;

[0012]FIG. 1c is a partially-fabricated embodiment of the semiconductordevice in FIG. 1b, after trench formation;

[0013]FIG. 1d is a partially-fabricated embodiment of the semiconductordevice in FIG. 1c, after metal layer #2 deposition;

[0014]FIG. 1e is a partially-fabricated embodiment of the semiconductordevice in FIG. 1d, after the addition of an etch-stop interposedinterlayer dielectric which is provided with vias;

[0015]FIG. 1f is a partially-fabricated embodiment of the semiconductordevice in FIG. 1e, after the addition of a trench-patterned photoresistlayer;

[0016]FIG. 1g is a partially-fabricated embodiment of the semiconductordevice in FIG. 1f, after trench formation;

[0017]FIG. 1h is a partially-fabricated embodiment of the semiconductordevice in FIG. 1g, after metal layer #3 deposition;

[0018]FIG. 1i is a fully-fabricated embodiment of the semiconductordevice in FIG. 1h, after the deposition of metal layers #4 and #5;

[0019]FIG. 2a is a color representation of a composite plan view of oneembodiment of an multi-layer interdigitated MiM capacitor, including acolor-coded key describing selected layers of preselected regions;

[0020]FIG. 2b is a plan illustration of the metal layer #1 (M1) of thecapacitor in FIG. 2a;

[0021]FIG. 2c is a plan illustration of the via layer #1 (V1) of thecapacitor in FIG. 2a;

[0022]FIG. 2d is a plan illustration of the metal layer #2 (M2) of thecapacitor in FIG. 2a;

[0023]FIG. 2e is a plan illustration of the via layer #2 (V2) of thecapacitor in FIG. 2a;

[0024]FIG. 2f is a plan illustration of the metal layer #3 (M3) of thecapacitor in FIG. 2a;

[0025]FIG. 2g is a plan illustration of the via layer #1 (V3) of thecapacitor in FIG. 2a;

[0026]FIG. 2h is a plan illustration of the metal layer #4 (M4) of thecapacitor in FIG. 2a;

[0027]FIG. 2i is a plan illustration of the via layer #4 (V4) of thecapacitor in FIG. 2a;

[0028]FIG. 2j is a plan illustration of the metal layer #5 (M5) of thecapacitor in FIG. 2a;

[0029]FIG. 3a is a color representation of a composite plan view of asecond embodiment of an multi-layer interdigitated MiM capacitor,including a color-coded key describing selected layers of preselectedregions;

[0030]FIG. 3b is a plan illustration of the metal layer #1 (Ml) of thecapacitor in FIG. 3a;

[0031]FIG. 3c is a plan illustration of the via layer #1 (V1) of thecapacitor in FIG. 3a;

[0032]FIG. 3d is a plan illustration of the metal layer #2 (M2) of thecapacitor in FIG. 3a;

[0033]FIG. 3e is a plan illustration of the via layer #2 (V2) of thecapacitor in FIG. 3a;

[0034]FIG. 3f is a plan illustration of the metal layer #3 (M3) of thecapacitor in FIG. 3a;

[0035]FIG. 3g is a plan illustration of the via layer #1 (V3) of thecapacitor in FIG. 3a;

[0036]FIG. 3h is a plan illustration of the metal layer #4 (M4) of thecapacitor in FIG. 3a;

[0037]FIG. 3i is a plan illustration of the via layer #4 (V4) of thecapacitor in FIG. 3a;

[0038]FIG. 3j is a plan illustration of the metal layer #5 (M5) of thecapacitor in FIG. 3a;

[0039]FIG. 4a is a color representation of a composite plan view of athird embodiment of an multi-layer interdigitated MiM capacitor,including a color-coded key describing selected layers of preselectedregions;

[0040]FIG. 4b is a plan illustration of the metal layer #1 (M1) of thecapacitor in FIG. 4a;

[0041]FIG. 4c is a plan illustration of the via layer #1 (V1) of thecapacitor in FIG. 4a;

[0042]FIG. 4d is a plan illustration of the metal layer #2 (M2) of thecapacitor in FIG. 4a;

[0043]FIG. 4e is a plan illustration of the via layer #2 (V2) of thecapacitor in FIG. 4a;

[0044]FIG. 4f is a plan illustration of the metal layer #3 (M3) of thecapacitor in FIG. 4a;

[0045]FIG. 4g is a plan illustration of the via layer #1 (V3) of thecapacitor in FIG. 4a;

[0046]FIG. 4h is a plan illustration of the metal layer #4 (M4) of thecapacitor in FIG. 4a;

[0047]FIG. 4i is a plan illustration of the via layer #4 (V4) of thecapacitor in FIG. 4a;

[0048]FIG. 4j is a plan illustration of the metal layer #5 (M5) of thecapacitor in FIG. 4a;

[0049]FIG. 5a is a color representation of a composite plan view of anmulti-layer grid array MiM capacitor, including a color-coded keydescribing selected layers of preselected regions;

[0050]FIG. 5b is a plan illustration of the metal layer #1 (M1) of thecapacitor in FIG. 5a;

[0051]FIG. 5c is a plan illustration of the via layer #1 (V1) of thecapacitor in FIG. 5a;

[0052]FIG. 5d is a plan illustration of the metal layer #2 (M2) of thecapacitor in FIG. 5a;

[0053]FIG. 5e is a plan illustration of the via layer #2 (V2) of thecapacitor in FIG. 5a;

[0054]FIG. 5f is a plan illustration of the metal layer #3 (M3) of thecapacitor in FIG. 5a;

[0055]FIG. 5g is a plan illustration of the via layer #1 (V3) of thecapacitor in FIG. 5a;

[0056]FIG. 5h is a plan illustration of the metal layer #4 (M4) of thecapacitor in FIG. 5a;

[0057]FIG. 5i is a plan illustration of the via layer #4 (V4) of thecapacitor in FIG. 5a; and

[0058]FIG. 5j is a plan illustration of the metal layer #5 (M5) of thecapacitor in FIG. 5a.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0059] Devices, including capacitors, according to the present inventionare intended to be easily and inexpensively implemented in copperdual-damascene processes, using existing process steps. The capacitorsare fully CMOS logic process compatible, and are amenable todeep-submicron (<0.13 μm) processing. Although the present invention isdescribed in the context of metal-insulator-metal capacitors, theteachings of the invention herein also can include otherconductor/dielectric devices, including, without limitation, anti-fusedevices. Further, other conductive materials, including for example,conductive polymers may be used in addition to metals.

[0060] Damascene process refers to a fabrication process sequence inwhich a pattern of interconnects is first etched into an interleveldielectric layer such as, for example, silicon dioxide. This dielectriclayer may be deposited on a barrier layer used to prevent the metal fromdiffusing into the silicon substrate. A thin “seed” layer is then usedfor depositing the metal in the etched pattern to create theinterconnects. Finally, the surface is polished back even with thesurface, typically by chemical mechanical polishing (CMP). Dualdamascene is a variation whereby intersecting troughs in the sameinterlevel dielectric are sequentially etched and concurrentlybackfilled with a metal stack. The trough overfill is then polished backto a planar surface, leaving an inlaid metal trace. The dual damasceneprocess can be used for forming the multilevel conductive lines ofmetal, such as copper, in the insulating layers of multi-layersubstrates on which semiconductor devices are mounted. The term “dual”refers to the formation of a second channel, a via 5000 to 7000 Å deep,within the trench. Existing dual damascene processes utilize silicondioxide as the insulator between the substrate and the conductive path,as well as between conductive paths. Also, the conventional dualdamascene process uses silicon nitride as an etch stop to preventdistortion of the via size during the final etch step. The final etchstep is generally used to create the via, as well as the interconnectiontrench, prior to filling the via and interconnection with a conductivematerial. The use of silicon nitride as an etch stop and a conventionalphoto-resist to define the trench in the second insulative layer canprovide for very high selectivity for the etch process.

[0061] Several different dual-damascene approaches have beeninvestigated, for example, the via-first technique, the trench-first andthe buried-via technique, a self-aligned process. For the purposes ofillustration, MiM capacitors according to the present invention aredescribed in the context of the via-first copper dual damasceneapproach, although those skilled in the art will recognize that theinvention is not so limited, but may be realized using other metals andother damascene techniques, in light of the teachings herein.

[0062]FIGS. 1a-1 i illustrate semiconductor device 100 in the form of acapacitor, in particular, a conductor-insulator-conductor capacitor,according to the present invention. Although the invention herein isimplemented as a metal-insulator-metal (MiM) capacitor in a dualdamascene fabrication process, the principles of using an etch stoplayer as the insulation layer in a conductor-insulator-conductorcapacitor can be implemented in other processes as well, including, forexample, single damascene and subtractive etch processes. Adual-damascene process can provide savings relative to single damasceneprocesses because only one metal fill step and one chemical mechanicalpolishing step are required for each level of conductor, and the wiringlevel and interlevel connections are created with a single polishingstep. Numerous dual-damascene process schemes exist but, overall, theseschemes may be classified into “via first” or “trench first,” dependingupon which pattern, via or trench, is initially delineated. Althoughdescribed herein in the context of a via-first scheme, it will beunderstood that the present invention also can be realized using atrench-first scheme.

[0063] In the via-first sequence, the via is masked and etched throughthe two layers of dielectric. The photomasking process for thesubsequent trench etch must expose and cleanly develop a trench patternin resist that has flooded the deep via. Typically, the via is coveredby a photoresist or organic plug that protects the via and theunderlying via nitride. Then the trench mask is aligned with the viahole and etched through the top layer of dielectric stopping on thefirst nitride layer. Finally, the nitride is etched at the bottom of thevia to expose the underlying copper line. In the standard dual damasceneprocess, the insulating layer is coated with a photoresist which isexposed through a first mask with image pattern of the via openings andthe pattern is anisotropically etched in the upper half of theinsulating layer. The photoresist now is exposed through a second maskwith an image pattern of the conductive line openings, after beingaligned with the first mask pattern to encompass the via openings. Inanisotropically etching the openings for the conductive lines in theupper half of the insulating material, the via openings already presentin the upper half are simultaneously etched and replicated in the lowerhalf of the insulating material. After the etching is complete, both thevias and line openings are filled with metal. Then, the surface of themetal layer is planarized, preferably using chemical-mechanicalpolishing process, although etch-back and capping methods also suitablefor planarization.

[0064] It is desirable that a “hard mask” etch barrier film, fabricatedof for example, silicon dioxide or silicon nitride, be used to preventthe upper trench patterns of dual damascene from being etched through,particularly if the layer underlying the insulation layer is the devicecontact or via area. Other barrier films may be used, however siliconnitride is preferred because silicon nitride, having a dielectricconstant of about 7.0, allows a selective etch process with respect todifferent underlying materials. Spin-on-glass, plasma nitride are alsosuitable as etch stop materials, for example, when polyimide layers areused. The silicon nitride etch stop barrier can be deposited using, forexample, Plasma Enhanced Chemical Vapor Deposition (PECVD) such that ithas a thickness between about 10 to 2000 angstroms.

[0065] Thus, in the dual-damascene process, there usually is adielectric layer deposited on top of a metal layer, which acts as anetch-stop layer for a via etch. Typically, this dielectric layer isremoved during a subsequent metal trench etch. However, if the design isvaried such that a via layer is drawn without having a metal layer ontop of it, the etch-stopping layer can be used as a field dielectricbetween the bottom metal and the via layer, to form ametal-insulator-metal (MiM) capacitor.

[0066] In a via-first dual-damascene process, the via is masked andetched through two layers of dielectric using a high-aspect ratio (HAR)etch, stopping at a hard mask or etch stop layer which lies beneath thevia. Then, a trench pattern is aligned with the via hole, and a trenchis etched into the dielectric surrounding the via hole. Finally, theetch stop layer is removed, and the conductor material is deposited inthe via and trench and is substantially planarized and polished.Dual-damascene processes can present significant fabrication challenges.Therefore, to contain product costs, it is desirable to minimize theaddition of processing steps during device manufacturing. Prior artmetal-insulator-metal capacitors (MiM), particularly those fabricatedusing dual-damascene process, often require additional processing steps,including HAR etches, vertical wall definition and deposition, and thelike, which can lead to greatly reduced product yields and substantialcost. In prior art dual damascene processes, the etch stop layer may beconsidered to be a hindrance to MiM fabrication. According to thepresent invention, a hard mask or etch stop layer, deposited by standarddeposition techniques, can be employed as the insulator in acapacitor-like structure, including capacitors and antifuses.

[0067] In FIGS. 1a-1 i, a cross-sectional model of an embodiment of thepresent invention is described during the fabrication of a five-layermetal device 100, where like numbers are representative of likestructures, regions, and components. In FIG. 1a, a conductive barrier isformed upon substrate 102 of semiconductor device 100, using dielectriclayer 104 and dielectric diffusion barrier 106. The conductive barrierprevents conductor (metal) ions from invading substrate 102,disadvantageously altering its electrical properties. Next, interlayerdielectric layer #1 (ILD1) 108 is deposited upon barrier layer 106using, for example, chemical vapor deposition (CVD), physical vapordeposition (PVD), and electrochemical vapor deposition (EVD) techniques.ILD1 (and subsequently-deposited ILD layers) can be manufactured oflow-k (k<about 5.0) materials, such as silicate-based ILDs including,for example, fluorinated (SiOF-FSG), carbon-doped (SiOC2-CSG),hydrogen-doped (HSG), and undoped (SiO2-USG) silicon dioxide glass, andcombinations thereof, as well as organic polymer-based ILDs such asSiLK, from Dow Chemical (Midland, Mich.), and FLARE and HOSP fromHoneywell Corp., Sunnyvale, Calif., and combinations.

[0068] Wells 105, 107 are etched into ILD1 108, stopping the etch backat layer 109, using standard photolithography and etching processes. Toprevent copper contamination of ILD1 108, metal barrier layer 111 isdeposited within the via well 105, and metal barrier layer 121 isdeposited within the core well 107. Suitable diffusion barrier metalscan include, for example, Ta/TaN. With wells 105, 107 thus formed, thevoids of wells 105, 107 are completely filled with metal (M1 layer), asis represented by conductor plugs 110, 112. The conductor material oflayer M1 (as well as subsequent via and metal layers) can be, forexample, Al, Cu, W, Ti, TiN, or silicides, with Cu frequently being usedin the popular Cu dual damascene process. In general, the M1 layer, andin particular, plugs 110, 112 serve as the lower electrical contact fordevice 100.

[0069] After the formation of the M1 layer, the surface overburden ofdevice 100 is removed using, for example, chemical mechanical polishing(CMP), or selective reactive ion etching (sRIE). Next, etch stop layer#1 (ES1) 114 is deposited upon ILD1 layer 108 and conductor plugs 110,112. ES1 can be composed of SiN, SiC, phosphosilicate glass (PSG), andthe like. It is desirable that the etch stop material of ES1, andsubsequent etch stop layers, possess a higher dielectric constant (k)than the ILD layers. Indeed, it is advantageous to employ low-kmaterials (e.g., k<about 5.0) for ILD, and to employ materialspossessing a higher k (>about 5.0) for etch stop layers. For example,silicon nitride can have a dielectric constant of between about k=5.5 toabout k=9.0, and generally about k=7.0, depending upon layer fabricationmethods, etc.

[0070] Continuing in FIG 1 a, interlayer dielectric layer #2 (ILD2) 116is then formed upon ES1 114, with etch stop layer #2 (ES2) 119 beingsuitably disposed therein. ES2 also can be composed of SiN, SiC,phosphosilicate glass (PSG), and the like, as is ES1. ILD2 116 isdesired to possess a lower dielectric constant than, and practicaldifferential etch characteristics relative to, ES1 114 and ES2 119.Patterns (not shown) are then formed on the surface of ILD2 116, withvia well 118 and core well 120 being etched into ILD2 116, through ES2119, and stopping at ES1 114.

[0071] Although conductor plugs 110, 112 are shown as being separateentities, the M1 layer also can be formed as a contiguous conductivelayer, for example, as a monolithic layer over an entire wafer, or aunitary layer with respect to one or more devices, depending upon thedevice design. Additional exemplary embodiments of M1 configurations areillustrated in FIGS. 2b, 3 b, 4 b, and 5 b. In certain embodiments ofthe present invention, plugs 110, 112 form the lower-most electrode ofthe capacitor, or antifuse, formed thereby. In particular embodiments,it may desirable to form the lowermost electrode with set apartportions, spatially arranged in a predetermined relationship, in orderto gain the advantage of the additional capacitance inherent in theportion of the dielectric layer disposed between the set-apart portionsof the electrode. Such an arrangement is exemplified in FIG. 1a, where aportion of interlayer dielectric layer #1 (ILD1) 108 is disposed betweenplugs 110, 112. Thus far, device 100 in FIG. 1a has been prepared usingan exemplary via-first dual damascene process.

[0072] In FIG. 1b, preparation is made to create a first trenchcontiguous with via well 118. To that end, photoresist layer 122 isdeposited upon ILD2 116, with trench pattern 124 therein being alignedto, and in communication with, first via well 118. In prior art, dualdamascene processes, including those forming MiM capacitors, all wellsin the interlevel dielectric typically have trench patterns respectivelyaligned thereto, including core well 120, allowing the etch stop layerdirectly inferior to the well to be removed. In the method of thepresent invention, however, photoresist layer 122 is caused tosubstantially fill core well 120, such that the portion of ES2 114,which is directly inferior thereto, is shielded from the subsequent etchstep.

[0073]FIG. 1c illustrates device 100 subsequent to etching, and afterphotoresist layer 122, seen in FIG. 1b, has been stripped away. Duringthis partial etch step, trench well 126 is formed superior and adjacentto first via well 118, by etching back ILD2 116 until ES2 119 isreached. Subsequently, exposed ES1 114 within first well 118 is etchedback, such that well 118 communicates with the M1 layer via plug 110.The region of ES1 114 inferior to capacitor well 120 remainssubstantially intact, due to the protective effect of photoresist layer122 during the etch process.

[0074] In FIG. 1d, device 100 is illustrated after the deposition of asecond conductor (metal-M2) layer. In preparation for M2 deposition,thin layers of barrier metal 113, 123, 141 are deposited upon walls ofvia well 118, trench well 126, and capacitor core well 120,respectively. Then, wells 118, 120, 126 are completely filled withconductor metal, forming V1 via 128, M2 trench plug 130, and M2capacitor plug 132. Using the dual damascene process, layers V1 and M2are effectively deposited in the same backfilling step. After theformation of the V1/M2 layer, the surface overburden of device 100 againis removed using, for example, chemical mechanical polishing (CMP), orselective reactive ion etching (sRIE). A skilled practitioner wouldrealize that FIG. 1d illustrates the basic components of aconductor-insulator-conductor capacitor in the form of conductor plug112, etch stop layer 114, and conductor plug 132, respectively. In FIG.1d, the spatial relationships between 110 and 112 can be selected toprovide additional capacitance using the inherent capacitivecharacteristics of ILD1 108. Thus, conductive regions 110, 112, 128, and130 can form the lower plate capacitor, conductive region 132 the upperplate, and ES1 114 can be the primary capacitor dielectric. A skilledartisan also would realize that by selecting the geometries of, and thespatial relationships between, components 110, 112, 130 and 132, thetotal capacitance of device 100 can further be adjusted or “tuned,”using the inherent capacitive characteristics of ILD1 108, and ILD2 116.

[0075]FIG. 1e shows device 100 after formation of second via well 138and capacitor conductor well 140. Following deposition andplanarization/polishing of the V1/M2 layer, etch stop layer #3 (ES3) 134is deposited thereupon. In addition, Interlayer dielectric layer #4(ILD4) 146 is deposited, with etch stop layer #4 (ES4) 149 beingdisposed therein. The surface of device 100 then is patterned (notshown) to permit the formation of via well 138 and conductor well 140during an etching process, which penetrates though ES4 149 but whichleaves ES3 134 essentially intact.

[0076] In FIG. 1f, photoresist layer 142, similar to layer 122 in FIG.1b, is applied to the surface of device 100, preferably filling well 140to protect the portion of ES3 134 disposed thereunder, and providingtrench pattern 144 which is aligned to, and in communication with, viawell 138.

[0077]FIG. 1g illustrates device 100 subsequent to etching, and afterphotoresist layer 142, seen in FIG. 1f, has been stripped away. This issimilar to the state of device 100 in FIG. 1c, after trench 126 has beenformed and photoresist layer 122 stripped away. During this partial etchstep, trench well 146 is formed superior and adjacent to via well 138,by etching back ILD4 136 until ES3 134 is reached. Subsequently, exposedES3 134 within first well 138 is etched back, such that well 138communicates with the M2 layer via plug 130. The region of ES3 134inferior to capacitor well 140 remains substantially intact, due to theprotective effect of photoresist layer 142 during the etch process.

[0078] In FIG. 1h, device 100 is illustrated after the deposition of athird conductor (metal-M3) layer. In preparation for M3 deposition, thinlayers of barrier metal 133, 143, 151 are deposited upon walls of viawell 138, trench well 146, and capacitor core well 140, respectively.Then, wells 138, 140, 146 are completely filled with conductor metal,forming V2 via 148, M3 trench plug 150, and M3 capacitor plug 152. Usingthe dual damascene process, layers V2 and M3 are effectively depositedin the same backfilling step. After the formation of the V2/M3 layer,the surface overburden of device 100 again is removed using, forexample, chemical mechanical polishing (CMP), or selective reactive ionetching (sRIE).

[0079] In FIG. 1i, device 100 is illustrated after 4th and 5th conductorlayers, metal M4 and M5, respectively, are deposited. Using processessimilar to those described with respect to FIGS. 1a-1 h, ES5 154 andILD5 156, having ES6 159 disposed therein, are deposited and then etchedback to permit deposition of M4 capacitor plug 162, V3 via 158, and M4trench 160. Also, layers ES7 164 and ILD6 166, having ES8 169 disposedtherein, are deposited and then etched back to permit deposition of M5capacitor plug 172, 43 via 168, and M5 trench 170. Finally, inner(upper) capacitor lead 174 and outer (lower) capacitor lead 176 areelectrically connected with plug 172 and plug 170, respectively.

[0080]FIGS. 2a-2 j are representative of the metal components of oneembodiment of an interdigitated capacitor 200 according to the presentinvention, using a five metal layer process. FIG. 2a is a color drawingrepresentative of a composite plan view of capacitor 200. A color legendto the right of device 200 in FIG. 2a is descriptive of the one or moremetal and/or via layers associated with the keyed structure. In thedescription herein, it is to be understood that there exists an etchstop layer between each successive layer of metal, unless interconnectedby an intervening via layer, similar to the composite structureillustrated in FIGS. 1a-1 i. Region 201, a capacitor lead, comprises M4metal layer. Region 202 represents a layering of M1, V1, M2, V2, M3, andM5. Region 203 represents a layering of V2, M3, and M4. In region 204,as well as similarly-keyed regions, the represented layers include V1and V3. In region 205, as well as similarly-keyed regions, therepresented layers include M1, V2, and V4. In region 206, as well assimilarly-keyed regions, the represented layers include M1, V1, M2, V2,M3, V3, M4, V4, and M5. In region 207, as well as similarly-keyedregions, the represented layer includes M1 only. In region 208, as wellas similarly-keyed regions, the represented layers include M1, V1, M2,M3, V3, M4, and M5. In region 209, as well as similarly-keyed regions,the represented layers include M1 and M5. In region 210, as well assimilarly-keyed regions, the represented layers include M1, M2, M3, M4,and M5. Region 211, another capacitor lead includes primarily M5material. Again, a layer of etch-stop material is desired to beinterposed between successive metal layers, for example, M1, ES1, M2,ES3, M3, ES5, M4, ES7, and M5.

[0081] In view of the above, FIGS. 2b-2 j illustrate the regions ofparticular metal/via layers which can be stacked vertically to formdevice 200 in FIG. 2a. As noted above, a layer of etch stop material,such as, for example, SiC, SiN, PSG, and the like, is interposed betweenadjacent metal layers. In device 200, metal layer M1 is represented bystructure 212 in FIG. 2b, via layer V1 is represented by structure 214in FIG. 2c, metal layer M2 is represented by structure 216 in FIG. 2d,via layer V2 is represented by structure 218 in FIG. 2e, metal layer M3is represented by structure 220 in FIG. 2f, via layer V3 is representedby structure 222 in FIG. 2g, metal layer M4 is represented by structure224 in FIG. 2h, via layer V4 is represented by structure 226 in FIG. 2i,and metal layer M5 is represented by structure 228 in FIG. 2j. Returningto FIG. 2a, regions 201 are comprised primarily of metal layer M4 whichcorresponds to structure 224 in FIG. 2h. Regions 202 are comprisedprimarily of M1 212, V1 214, M2 216, V2 218, M3 220, and M5 228. Regions203 are comprised primarily of V2 218, M3 220, and M4 224. Regions 204are comprised primarily of V1 214 and V3 222. Regions 205 are comprisedprimarily of M1 212, V2 218, and V4 226. Regions 206 are comprisedprimarily of M1 212, V1 214, M2 216, V2 218, M3 220, V3 222, M4 224, V4226, and M5 228. Regions 207 is comprised primarily of M1 212. Regions208 are comprised primarily of M1 212, V1 214, M2 216, M3 220, V3 222,M4 224, and M5 228. Regions 209 are comprised primarily of M1 212 and M5228. Regions 210 are comprised primarily of M1 212, M2 216, M3 220, M4224, and M5 228. Region 211, another capacitor lead is comprisedprimarily of M5 228 material.

[0082] A skilled artisan would realize that interposed between layer M1212, layer M2 216, layer M3 220, layer M4 224, and layer M5 228 areinterposed etch stop layers similar to layers 114, 134, 154, and 164, inFIG. 1i. As noted above, this etch stop material can be, for example,SiC, SiN, PSG, and the like, which generally possesses a higherdielectric constant, k, than adjacent ILD material. Vias selectivelypenetrate the aforementioned etch stop layers to created predeterminedconductive paths within device 200. Via structure V1 214 providesconductive path between metal layer M1 212 and metal layer M2 216selectively being deposited in patterns etched through the etch stoplayer interposed between M1 212 and M2 216. Similarly, via layer V2 218provides a conductive path between layers M2 216 and M3 220 because ofthe selective removal of the etch stop layer interposed between layer M2216 and M3 220. Likewise, via layer V3 222 provides selective conductivepaths between metal layer M3 220 and metal layer M4 224 by way ofselective removal of the etch stop layer interposed between layer M3 220and metal layer M4 224. Finally, via layer V4 provides selectiveconductive paths between metal layer M4 224 and metal layer M5 228 byselective removal of the etch stop layer interposed between metal layerM4 224 and metal layer M5 228.

[0083]FIGS. 3a-3 j are representative of the metal components of anotherembodiment of an interdigitated capacitor 300 according to the presentinvention, using a five metal layer process. FIG. 3a is a color drawingrepresentative of a composite plan view of capacitor 300. A color legendto the right of device 300 in FIG. 3a is descriptive of the one or moremetal and/or via layers associated with the keyed structure. In thedescription herein, it is to be understood that there exists an etchstop layer between each successive layer of metal, unless interconnectedby an intervening via layer, similar to the composite structureillustrated in FIGS. 1a-1 i. Region 301, a capacitor lead, comprises M4metal layer. Region 302 represents a layering of M1, V1, M2, V2, M3, andM5. In region 303, as well as similarly-keyed regions, the representedlayers include M1 and V4. In region 304, as well as similarly-keyedregions, the represented layers include V2, M3, and M4. In region 305,as well as similarly-keyed regions, the represented layers include V1and V3. In region 306, as well as similarly-keyed regions, therepresented layers include M1, V1, M2, V2, M3, V3, M4, V4, and M5. Inregion 307, as well as similarly-keyed regions, the represented layerincludes M1 only. In region 308, as well as similarly-keyed regions, therepresented layers include M1, V2, and V4. In region 309, as well assimilarly-keyed regions, the represented layers include M1, M2, M3, M4,and M5. In region 310, as well as similarly-keyed regions, therepresented layers include M1, V1, M2, M3, V3, M4, and M5. Region 311,another capacitor lead, includes primarily M5 material.

[0084] In view of the above, FIGS. 3b-3 j illustrate the regions of theparticular metal/via layers which can be stacked vertically to formdevice 300 in FIG. 3a. In device 300, metal layer M1 is represented bystructure 312 in FIG. 3b, via layer V1 is represented by structure 314in FIG. 3c, metal layer M2 is represented by structure 316 in FIG. 3d,via layer V2 is represented by structure 318 in FIG. 3e, metal layer M3is represented by structure 320 in FIG. 3f, via layer V3 is representedby structure 322 in FIG. 3g, metal layer M4 is represented by structure324 in FIG. 3h, via layer V4 is represented by structure 326 in FIG. 3i,and metal layer M5 is represented by structure 328 in FIG. 3j. Returningto FIG. 3a, regions 301 are comprised primarily of metal layer M4, whichcorresponds to structure 324 in FIG. 3h. Regions 302 are comprisedprimarily of M1 312, V1 314, M2 316, V2 318, M3 320, and M5 328. Regions303 are comprised primarily of M1 312 and V4 326. Region 304 arecomprised primarily of V2 318, M3 320, and M4 324. Regions 305 includeprimarily V1 314, and V3 322. Regions 306 are comprised primarily of M1312, V1 314, M2 316, V2 318, M3 320, V3 322, M4 324, V4 326 and M5 328.Regions 307 are comprised primarily of M1 312. Regions 308 are comprisedprimarily of M1 312, V2 318, and V4 326. Regions 309 are comprisedprimarily of M1 312, M2 316, M3 320, M4 324, and M5 328. Regions 310 arecomposed primarily of M1 312, V1 314, M2 316, M3 320, V3 322, M4 324,and M5 328. Region 311 is composed primarily M5 328.

[0085] A skilled artisan would realize that interposed between layer M1312, layer M2 316, layer M3 320, layer M4 324, and layer M5 328 areinterposed etch stop layers similar to layers 114, 134, 154, and 164, inFIG. 1i. As noted above, this etch stop material can be, for example,SiC, SiN, PSG, and the like, which generally possesses a higherdielectric constant, k, than adjacent ILD material. Vias selectivelypenetrate the aforementioned etch stop layers to create predeterminedconductive paths within device 300. For example, via structure V1 314provides conductive path between metal layer M1 312 and metal layer M2316 selectively being deposited in patterns etched through the etch stoplayer interposed between M1 312 and M2 316. Similarly, via layer V2 318provides a conductive path between layers M2 316 and M3 320 because ofthe selective removal of the etch stop layer interposed between layer M2316 and M3 320. Likewise, via layer V3 322 provides selective conductivepaths between metal layer M3 320 and metal layer M4 324 by way ofselective removal of the etch stop layer interposed between layer M3 320and metal layer M4 324. Finally, via layer V4 provides selectiveconductive paths between metal layer M4 324 and metal layer M5 328 byselective removal of the etch stop layer interposed between metal layerM4 324 and metal layer M5 328.

[0086]FIGS. 4a-4 j are representative of the metal components of yetanother embodiment of a multi-layer interdigitated capacitor 400according to the present invention, using a five metal layer process.FIG. 4a is a color drawing representative of a composite plan view ofcapacitor 400. A color legend to the right of device 400 in FIG. 4a isdescriptive of the one or more metal and/or via layers associated withthe keyed structure. In the description herein, it is to be understoodthat there exists an etch stop layer between each successive layer ofmetal, unless interconnected by an intervening via layer, similar to thecomposite structure illustrated in FIGS. 1a-1 i. Region 401, a capacitorlead, comprises M4 metal layer. Region 402, as well as similarly-keyedregions, represent a layering of M1, V1, M2, V2, M3, and M5. In region403, as well as similarly-keyed regions, the represented layers includeM1, V1, M2, M3, V3, M4 and M5. In region 404, as well as similarly-keyedregions, the represented layers include M1 and V4. In region 405, aswell as similarly-keyed regions, the represented layers include M3 andM4. In region 406, as well as similarly-keyed regions, the representedlayers include V1 and V3. In region 407, as well as similarly-keyedregions, the represented layer includes V2 only. In region 408, as wellas similarly-keyed regions, the represented layers include M1, V1, M2,V2, M3, V3, M4, V4, and M5. In region 409, as well as similarly-keyedregions, the represented layers include M1. In region 410, as well assimilarly-keyed regions, the represented layers include M1, V2, and V4.In region 411, as well as similarly-keyed regions, the representedlayers include M1, V1, V3, and V4. In region 412, as well assimilarly-keyed regions, the represented layers include M1, M2, M3, M4,and M5. Region 413, another capacitor lead, includes primarily M5material.

[0087] In view of the above, FIGS. 4b-4 j illustrate the regions of theparticular metal/via layers which can be stacked vertically to formdevice 400 in FIG. 4a. In device 400, metal layer M1 is represented bystructure 412 in FIG. 4b, via layer V1 is represented by structure 414in FIG. 4c, metal layer M2 is represented by structure 416 in FIG. 4d,via layer V2 is represented by structure 418 in FIG. 4e, metal layer M3is represented by structure 420 in FIG. 4f, via layer V3 is representedby structure 422 in FIG. 4g, metal layer M4 is represented by structure424 in FIG. 4h, via layer V4 is represented by structure 426 in FIG. 4i,and metal layer M5 is represented by structure 428 in FIG. 4j. Returningto FIG. 4a, region 401 is comprised primarily of metal layer M4, whichcorresponds to structure 324 in FIG. 3h. Regions 402 are comprisedprimarily of M1 412, V1 414, M2 416, V2 418, M3 420, and M5 328. Regions403 are comprised primarily of M1 412, V1 414, M2 416, M3 420, V3 422,M4 424 and M5 428. Regions 404 are comprised primarily of M1 412 and V4426. Regions 405 include primarily M3 420, and M4 424. Regions 406 arecomprised primarily of V1 414, and V3 422. Regions 407 are comprisedprimarily of V2 418. Regions 408 are comprised primarily of M1 412, V1414, M2 416, V2 418, M3 420, V3 422, M4 424, V4 426 and M5 428. Regions409 is comprised primarily of M1 412. Regions 410 are comprisedprimarily of M1 412, V2 418, and V4 426. Regions 411 are comprisedprimarily of M1 412, V1 414, V3 422, and V4 426. Regions 412 arecomprised primarily of M1 412, M2 416, M3 420, M4 424, and M5 428.Region 413 is composed primarily M5 428.

[0088] A skilled artisan would realize that between layer M1 412, layerM2 416, layer M3 420, layer M4 424, and layer M5 428 are interposed etchstop layers similar to layers 114, 134, 154, and 164, in FIG. 1i. Asnoted above, this etch stop material can be, for example, SiC, SiN, PSG,and the like, which generally possesses a higher dielectric constant, k,than adjacent ILD material. Vias selectively penetrate theaforementioned etch stop layers to create predetermined conductive pathswithin device 400. For example, via structure V1 414 provides conductivepath between metal layer M1 412 and metal layer M2 416 selectively beingdeposited in patterns etched through the etch stop layer interposedbetween M1 412 and M2 416. Similarly, via layer V2 418 provides aconductive path between layers M2 416 and M3 420 because of theselective removal of the etch stop layer interposed between layer M2 416and M3 420. Likewise, via layer V3 422 provides selective conductivepaths between metal layer M3 420 and metal layer M4 424 by way ofselective removal of the etch stop layer interposed between layer M3 420and metal layer M4 424. Finally, via layer V4 426 provides selectiveconductive paths between metal layer M4 424 and metal layer M5 428 byselective removal of the etch stop layer interposed between metal layerM4 424 and metal layer M5 428.

[0089]FIGS. 5a-5 j are representative of the metal components of oneembodiment of a multi-layer 3-dimensional array capacitor 500 accordingto the present invention, using a five metal layer process. FIG. 5a is acolor drawing representative of a composite plan view of capacitor 500.A color legend to the right of device 500 in FIG. 5a is descriptive ofthe one or more metal and/or via layers associated with the keyedstructure. In the description herein, it is to be understood that thereexists an etch stop layer between each successive layer of metal, unlessinterconnected by an intervening via layer, similar to the compositestructure illustrated in FIGS. 1a-1 i. Region 501, a capacitor lead,comprises M3 metal layer. Region 502 represents a layering of M1, M3,and M5. In region 503, as well as similarly-keyed regions, therepresented layers include M1, V1, V2, M3, V3, V4 and M5. In region 504,as well as similarly-keyed regions, the represented layers include M1and M5. In region 505, as well as similarly-keyed regions, therepresented layers include M1, V1, M2, V2, M3, V3, M4, V4, and M5. Inregion 506, as well as similarly-keyed regions, the represented layersinclude M1, M2, M3, M4, and M5.

[0090] In view of the above, FIGS. 5b-5 j illustrate the regions of theparticular metal/via layers which can be stacked vertically to formdevice 500 in FIG. 5a. In device 500, metal layer M1 is represented bystructure 512 in FIG. 5b, via layer V1 is represented by structure 514in FIG. 5c, metal layer M2 is represented by structure 516 in FIG. 5d,via layer V2 is represented by structure 518 in FIG. 5e, metal layer M3is represented by structure 520 in FIG. 5f, via layer V3 is representedby structure 522 in FIG. 5g, metal layer M4 is represented by structure524 in FIG. 5h, via layer V4 is represented by structure 526 in FIG. 5i,and metal layer M5 is represented by structure 528 in FIG. 5j. Returningto FIG. 5a, regions 501 are comprised primarily of metal layer M3, whichcorresponds to structure 520 in FIG. 5f. Regions 502 are comprisedprimarily of M1 512, M3 520, and M5 528. Regions 503 are comprisedprimarily of M1 512, V1 514, V2, 518, M3 520, V3 522, V4 526, and M5528. Region 504 are comprised primarily of M1 512 and M5 528. Regions505 are comprised primarily of M1 512, V1 514, M2 516, V2 518, M3 520,V3 522, M4 524, V4 526 and M5 528. Regions 506 comprised primarily of M1512, M2 516, M3 520, M4 524, and M5 528.

[0091] A skilled artisan would realize that interposed between layer M1512, layer M2 516, layer M3 520, layer M4 524, and layer M5 528 areinterposed etch stop layers similar to layers 114, 134, 154, and 164, inFIG. 1i. As noted above, this etch stop material can be, for example,SiC, SiN, PSG, and the like, which generally possesses a higherdielectric constant, k, than adjacent ILD material. Vias selectivelypenetrate the aforementioned etch stop layers to create predeterminedconductive paths within device 500. For example, via structure V1 314provides conductive path between metal layer M1 312 and metal layer M2316 selectively being deposited in patterns etched through the etch stoplayer interposed between M1 312 and M2 316. Similarly, via layer V2 318provides a conductive path between layers M2 316 and M3 320 because ofthe selective removal of the etch stop layer interposed between layer M2316 and M3 320. Likewise, via layer V3 322 provides selective conductivepaths between metal layer M3 320 and metal layer M4 324 by way ofselective removal of the etch stop layer interposed between layer M3 320and metal layer M4 324. Finally, via layer V4 provides selectiveconductive paths between metal layer M4 324 and metal layer M5 328 byselective removal of the etch stop layer interposed between metal layerM4 324 and metal layer M5 328.

[0092] Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed:
 1. A method of forming a metal-insulator-metalcapacitor on a substrate comprising: defining a first portion of one ormore layers formed on the substrate; forming a first well in the firstportion; applying a first diffusion barrier metal layer on the firstwell; forming a first conductive plug in the first well; forming anetch-stop layer on at least a portion of the first conductive plug, theetch-stop layer having a preselected dielectric constant and apredetermined geometry; defining a second portion of the one or morelayers adjacent the etch-stop layer; forming a second well in the secondportion to expose at least a portion of the etch-stop layer, applying asecond diffusion barrier metal layer on the second well and on anexposed portion of the etch-stop layer; and forming a second conductiveplug in the second well to provide the metal-insulator-metal capacitorwith the first conductive plug through the etch-stop layer.
 2. Themethod of claim 1, wherein the preselected dielectric constant is aboveabout 4.0.
 3. The method of claim 1, wherein the etch-stop layercomprises a silicon nitride having a preselected dielectric constant ofbetween about 5.5 and about 9.0.
 4. The method of claim 1, wherein atleast one of the first conductive plug and the second conductive plug isa metal.
 5. The method of claim 1, further comprising varying thespatial relationship between the first conductive plug and the secondconductive plug to vary the capacitance of the metal-insulator-metalcapacitor.